Definition:
A metagenome is all genetic material (i.e. all genes and genomes) from a defined environment. This includes DNA from living microorganisms, viruses, and cell-free DNA. The analysis of metagenomes is termed “metagenomics.” By isolating and sequencing total DNA from a sample and applying a range of bioinformatics tools, researchers can determine the community composition and encoded functions of the microorganisms inhabiting microbiomes.
Because marker-based species identification methods, such as 16S and 18S rRNA sequencing, target only one or a few genes, they are not considered metagenomic even when used to determine the composition of a microbial community.
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